cylinder head ventilation Options

[turbo2]

Folks,

Heard some where that when converting to carbs one better improve ventilation of the engine internals by installing vents in the cylinder heads connecting to an oil puke tank/bottle.

Why is this? as cant see how installing carbs will affect the crankcase pressure unless it's combined with a large increase in cylinder volume. The vent thru the filler neck should be good enough. Although know from my time tinkering with bikes that improving the crankcase ventilation could give 6-7 hp on a 150 hp motor so might be missing the obvious.

Nevertheless making a nice puke bottle of a guiness can which will seriously enhance the engine bay appearance.

Also if anyone have done this before would much appreciate a few pics as to where you fitted the vents.

Thanks in adv
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[Cap'n Krusty]

You'd have a better chance of getting a good answer if you told us what engine you have. '73-'74s (except 1.8s) had vented heads, and the bosses are there on '75-'76 heads. I find it easiest to install vents there if they're not already present. Enlightened people use a vent container made specifically for that purpose, and return the fumes to the engine. CB Performance and others sell a simple one, and there's a really elegant one available from someone here on the World. BTW, "road draft" venting systems have been illegal in the US since 1965. I would guess Canada has similar emissions laws.

The Cap'n

[Spoke]

I have a 1.8L that only has the bosses on the heads. What are the drawbacks of running DJET FI without having the head vents?

[Cap'n Krusty]

I have a 1.8L that only has the bosses on the heads. What are the drawbacks of running DJET FI without having the head vents?

If you use the early FI system, you'll be fine. If you use the closed system found on the '73-'74 cars, you'll blow oil past the crankshaft seals. BTDT. Not pretty, and it'll move a LOT of oil.

The Cap'n

[craig downs]

There was a heated thread a couple of months back on this topic. I would try to look it up lots of good info on not to add vents to the heads

[Bleyseng]

Even the Ljet 1.8's and 75-76 2.0L engines had a vent system it just came off the breather tower but the head vents were deleted. The crankcase pressure must go somewhere or you will blow out the seals.

[turbo2]

Even the Ljet 1.8's and 75-76 2.0L engines had a vent system it just came off the breather tower but the head vents were deleted. The crankcase pressure must go somewhere or you will blow out the seals.

All,

Thanks for input, the motor is a 1.8 and the breather on the filler neck will remain so if the motor hasn't blown any seals by now what difference will the carbs make? Also legality is not an issue where I live as we don't have emission or annual safety inspections here.

[Bleyseng]

The carbs don't make a difference its how you hook up where the hose from the breather goes. Djet used a strong vacuum at the plenum to pull the air and so did Ljet. sometimes a hose hooked to the air filter isn't enough vacuum.